Detailed notes from a student who achieved a grade 9 in Biology last year on:
Topic 1: Cell biology
Topic 2: Organisation
Topic 3: Infection and response
Topic 4: Bioenergetics
Topic 5: Homeostasis and response
Topic 6: Inheritance, variation and evolution
Topic 7: Ecology
TOPIC 1: CELL BIOLOGY
Topics:
● SECTION A: Cell structure
○ Eukaryotes and prokaryotes
○ Animal and plant cells
○ Cell specialisation
○ Cell differentiation
○ Microscopy
○ Binary fission
○ Culturing microorganisms
● SECTION B: Cell division
○ Chromosomes
○ Mitosis and the cell cycle
○ Stem cells
● SECTION C: Transport in cells
○ Diffusion
○ Osmosis
○ Active transport
, ell structure
→ SECTION A: C
Eukaryotes and Prokaryotes:
Eukaryotic cells: Prokaryotic cells:
● Complex and include all animal and plant ● Smaller and simpler compared to eukaryotic
cells ● Single-celled organism
● All eukaryotic cells have: ○ eg/ bacteria
○ Cell membrane ● 0.2 - 2.0 µm in length and 1 - 2 orders of
○ Cytoplasm magnitude smaller than eukaryotes
○ Genetic material (DNA) - enclosed in ● All prokaryotic cells have:
the nucleus ○ Cytoplasm
■ eg/ animals, plants, fungi ○ Cell membrane
and protista are all ○ Cell wall (not made of cellulose)
eukaryotes ○ Genetic material found free in
cytoplasm - chromosome is a single
DNA loop
○ Plasmids (extra small rings of DNA)
code for specific features such as
antibiotic resistance
○ Protective slime capsule
○ Flagella (protein strand that lashes
about to move)
Animal and Plant Cells:
→ All living organisms are made of cells
● Subcellular structures = different parts of a cell
● The structures of different types of cells are related to their specific function
● Plant and animal cells have similarities and differences
○ Animal cells → 10 to 30 µm long
○ Plant cells → 10 to 100 µm long
⇒ Found in animals and plant cells:
PART FUNCTION DIAGRAM
● Controls activities of cells
● Contains genetic material
Nucleus
● Surrounded by nuclear membrane
○ Average diameter = 10µm
● A liquid gel where chemical reactions occur
Cytoplasm
● Contains enzymes which control reactions
● Holds cell together
Cell membrane
● Controls passage of substances (eg/ glucose)
● Where aerobic respiration takes place
Mitochondria
● Releases energy that the cell requires
Ribosomes ● Where the protein synthesis takes place
, ound only in plant cells:
⇒F
PART FUNCTION DIAGRAM
● Rigid
Cell wall ● Made of cellulose
● Supports/strengthens cell
● A space in the cytoplasm filled with cell sap
Permanent ○ Cell sap = a weak solution of sugar and salts
vacuole ● Helps to keep cells rigid
● Supports the plant
● Found in green parts of plant
● Contain chlorophyll
○ ^ absorbs light so plant can make food by
Chloroplasts photosynthesis
● Around 3 - 5µm long
● Root cells don't need chloroplasts - they are
underground and don't photosynthesis
Cell Specialisation:
→ Cells have different structures to suit their different functions
● As an organism develops, cells differentiate t o form different types of cells
○ They differentiate to become specialised → it acquires different subcellular structures to enable it
to carry out a certain function
○ Most differentiation occurs as an organism develops
Animal cells: Plant cells:
● Differentiate at an early stage of ● Retain ability to differentiate throughout life
development ● Very specialised cells with clear adaptations
● Specialised cells used for repairing and for a particular job
replacing cells (eg/ skin and blood cells) ● Can be specialised to function within tissues,
● Can be specialised to function within tissues, organs, organ systems or whole organisms
organs, organ systems or whole organisms ○ eg/ root hair cells, photosynthetic
○ eg/ nerve cells, sperm cells, muscle cells, xylem cells, phloem cells
cells
⇒ Specialisation in animal cells:
CELL TYPE FUNCTION SPECIAL FEATURES
● Carries electrical impulses ● Lots of dendrites - make connections t o other nerve
around the body cells
● Provide rapid ● Long axon to carry nerve impulses
communication system ● Synapses = nerve endings - pass impulses to other
Nerve cell between different parts of cells using special transmitter chemicals
body ● Contain lots of mitochondria - energy needed to make
● Sends and receives signals chemicals
● Controls and coordinates ● Myelin sheath insulates impulse
actions
● Move and control our ● Smooth muscle cells contract to squeeze food through
Muscle cell
movements gut (digestive system)
, ● Can contract and relax in ● Striated muscle cells = contain special proteins that
pairs to move bones of slide to make fibres contract
skeleton ● Many mitochondria - transfers energy needed for
chemical reactions to take place as muscles relax and
contract
● Store glycogen - chemical is b roken down to be used
in cellular respiration
● Long - have space to contract
● Fertilises the ovum (egg cell) ● Long tail - helps move sperm through female
● Contain genetic info from reproductive system
male parent ● Streamlined head
● Moves through the female ● Middle section full of mitochondria - transfers energy
Sperm cell
reproductive system to to tail
reach an egg and break into ● Acrosome (head) - stores digestive enzymes which
it help break outer layer of egg
● Large nucleus - contains genetic information
pecialisation in plant cells:
⇒S
CELL TYPE FUNCTION SPECIAL FEATURES
● On the surface of plant roots ● Large SA - allows lots of water to move
● Help plant take up water/mineral ions into cell
more efficiently ● Large permanent vacuole - speeds up
Root hair cell
● Close to xylem cells movement of water by osmosis
● Mineral ions moved into root hair cells by ● Many mitochondria - transfer energy
active transport needed for active transport
● Allows plant to make food for itself ● Contain chloroplasts = specialized green
through process of photosynthesis structures
○ Contain chlorophyll - trap light
needed for photosynthesis
● Positioned in continuous layers in leaves
and outer stem to absorb as much light
Photosynthetic as possible
cell ● Large permanent vacuole
○ Helps keep cell rigid during
osmosis
○ Supports stem (forms
photosynthetic tissue)
○ Keeps leaves spread out to
capture light
● Xylem = transport tissue - carries ● Lignin builds up in spirals in cell walls -
water/mineral ions from roots to leaves causes xylem cells to die and form hollow
Xylem cell and shoots tubes which transport water/minerals
● Supports plant ● Spirals/rings of lignin withstand pressure
● Made up of xylem cells of water moving up plant
● Phloem = transport tissue - carries ● Cell walls between cells break to form
glucose made by photosynthesis around sieve plates - allow water carrying
plant dissolved food to move
Phloem cell ● Made from phloem cells ● Less internal structures to allow more
space for water
● Supported by companion cells - transfer
energy from mitochondria
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